Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/44—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications
  • C09D5/4419—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications with polymers obtained otherwise than by polymerisation reactions only involving carbon-to-carbon unsaturated bonds
  • C09D5/443—Polyepoxides
  • C09D5/4434—Polyepoxides characterised by the nature of the epoxy binder
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
  • C08G18/0804—Manufacture of polymers containing ionic or ionogenic groups
  • C08G18/0809—Manufacture of polymers containing ionic or ionogenic groups containing cationic or cationogenic groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/64—Macromolecular compounds not provided for by groups C08G18/42 - C08G18/63
  • C08G18/6415—Macromolecular compounds not provided for by groups C08G18/42 - C08G18/63 having nitrogen
  • C08G18/643—Reaction products of epoxy resins with at least equivalent amounts of amines
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/4007—Curing agents not provided for by the groups C08G59/42 - C08G59/66
  • C08G59/4014—Nitrogen containing compounds
  • C08G59/4021—Ureas; Thioureas; Guanidines; Dicyandiamides
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S524/00—Synthetic resins or natural rubbers -- part of the class 520 series
  • Y10S524/901—Electrodepositable compositions

Definitions

• the present invention relates to an adduct and its use as a cationic binder, especially for cathodic electrocoating.
• Aqueous dispersions or solutions--intended for surface coating--of resins containing cationic groups have been known for some time.
• Such products which can be deposited on a metallic workpiece wired as the cathode, offer particular advantages when used in electrocoating.
• cathodic electrocoating does not cause any problems of dissolution of the metal, the passivating layers remain undamaged, and the cationic coating as a rule improves the corrosion protection.
• Cathodic electrocoating agents have hitherto been based on water-dispersible or water-soluble resins possessing amine, ammonia, sulfonium or phosphonium groups.
• binders have the disadvantage that, if they carry quaternary ammonium groups, they can indeed be dissolved or dispersed, as salts, in water at a neutral to alkaline pH, but that after deposition as the quaternary ammonium base, and after baking (especially at the desired low baking temperatures), the polar groups largely persist.
• Polymers containing phosphonium groups and polymers containing sulfonium groups have the disadvantage that these groups are unstable in a neutral or alkaline electrocoating bath of the type the user wishes to employ.
• binders which can readily be converted, at a neutral to alkaline pH, to stable aqueous solutions or dispersions, especially for electrocoating baths, may be obtained by introduction of guanidine groups.
• a further advantage of the guanidine group is that on baking it can, by virtue of its high NH functionality, react--given a suitable crosslinking method, for example with free isocyanato groups formed from blocked isocyanate groups--to give non-ionic and hence substantially non-polar groups, or that it can decompose, under the action of water and heat, into CO 2 , ammonia and the corresponding primary or secondary amine, depending on the degree of substitution of the guanidine group.
• These amines are far less basic than the initial guanidine group.
• such amine groups cannot be converted to non-ionic, substantially non-polar, groups by suitable crosslinking methods (for example by reaction with isocyanate groups).
• the invention relates to an adduct which has been obtained by reacting
• the adduct may or may not be partially or completely neutralized by adding an acid. Furthermore, the novel adduct can contain blocked isocyanate groups.
• the present invention further relates to the use of the adduct according to the invention, with or without combination with a completely blocked polyisocyanate, an aminoplast resin and/or a phenoplast resin, as a binder in coating agents, and more specifically its use in aqueous coating agents for the cathodic electrocoating of metal articles, which coating agents may or may not additionally contain from 5 to 40, preferably from 15 to 30, % by weight, based on total binder, of a blocked polyisocyanate, an aminoplast resin and/or a phenoplast resin.
• an epoxide compound containing one or more epoxide groups preferably a glycidyl ether of a polyhydric alcohol or phenol
• suitable polyhydric alcohols are aliphatic alkanediols of 2 to 8 carbon atoms, alkanetriols, eg. glycerol, alkanetetrols, e.g. pentaerythritol and cycloaliphatic diols, e.g. bis-(4-hydroxycyclohexyl)-2,2-propane.
• Polyhydric polynuclear phenols, especially bisphenol A are however particularly preferred.
• the epoxide compound is reacted with guanidine, with a guanidine derivative, for example an alkylguanidine, eg. dimethylguanidine, or with a guanidinium salt derived from these.
• a guanidine derivative for example an alkylguanidine, eg. dimethylguanidine, or with a guanidinium salt derived from these.
• suitable guanidinium salts are guanidine carbonate, guanidine acetate, guanidine nitrate and the like.
• epoxide-free adducts which are preferred according to the invention, at least one mole of guanidine or of one of its salts is employed per epoxide group.
• the ratio of epoxide groups to guanidine must be carefully chosen to prevent premature crosslinking. If substantially less than one mole of guanidine is used per equivalent of epoxide group capable of reaction, an undesirably large proportion of epoxide groups remains in the binder and may lead to side-reactions.
• the preparation of the adduct may be carried out in the absence of solvents or in a suitable solvent, eg. dioxane, dimethylformamide or ethylene glycol, at from 10° to 150° C., preferably from 20° to 80° C.
• a resinous material for example based on reaction products of aliphatic or aromatic polyepoxy resins with polyols (for example with hydroxyl-containing polyurethanes, hydroxyl-containing polyethers and the like) or with polyphenols (for example reaction products of polyepoxides with an excess of bisphenol A), which resinous material has such a high residual epoxide functionality per individual molecule that reaction with guanidine (about 1 mole of guanidine per mole of residual expoxide content) does not cause crosslinking, but neutralization at a slightly acid pH or, preferably, at a pH above 7, renders the resin water-dispersible or water-soluble.
• polyols for example with hydroxyl-containing polyurethanes, hydroxyl-containing polyethers and the like
• polyphenols for example reaction products of polyepoxides with an excess of bisphenol A
• the amount of guanidine groups, relative to the remainder of the resinous substance, required to achieve the desired degree of solubilization may vary.
• the amount depends on the one hand on the molecular weight and on the other hand on the total structure of the end product, for example on the balance between hydrophilic or polar groups (hydroxyl, ether, amide or urethane groups) and hydrophobic units in the resin, leaving the guanidine modification out of account.
• the degree of modification with guanidine groups, the molecular weight and the structure of the resin starting material should be selected so as to give a stable dispersion or solution when a partially or completely neutralized product is mixed with an aqueous medium.
• the resin should be capable of cataphoretic deposition from the resulting dispersion or solution, to give a film which adheres firmly to the cathode and is no longer easily removable by rinsing with water.
• the parameters mentioned, namely structure, molecular weight and degree of modification with guanidine, are inter-related as far as the achievement of the desired final properties is concerned. For example, a lesser degree of modification with guanidine groups is needed if the resin has a higher content of other polar groups, eg. hydroxyl or ether groups.
• the selection of the optimum relations--for obtaining the desired properties--between molecular weight, structure of the starting resin and degree of modification with guanidine presents no difficulties to an expert.
• molecular weight range of from about 500 to 50,000 which is of interest for aqueous surface-coating binders and more specifically for electrocoating binders, from about 0.01 to 10 milliequivalents of guanidine groups as a rule suffice per gram of resin solids.
• the adduct obtained, containing substituted guanidine groups is advantageously at least partially neutralized with acid before use in an aqueous medium.
• This neutralization should provide from 0.1 to 1.5, preferably from 0.5 to 1.0, protons per guanidine group.
• the amount of acid depends on the number of guanidine groups introduced into the resin and on the pH required to solubilize or disperse the product in water.
• guanidine is hydroxyalkylated with epoxide compounds which contain hydroxyl groups which have been reacted with partially blocked polyisocyanates.
• partially blocked polyisocyanates are partially blocked toluylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate and more highly condensed polyisocyanates, eg. reaction products of 1 mole of ethylene glycol with 2 moles of isophorone diisocyanate or of 1 mole of trimethylolpropane with 3 moles of toluylene diisocyanate.
• suitable blocking agents are lactams, eg.
• ⁇ -caprolactam phenols, cresols, oximes, piperidone, piperidine, acetoacetic acid esters, malonic acid esters, alcohols and imidazoles.
• the polyisocyanates are only partially blocked, so that one isocyanate group remains free and is able to react with the hydroxyl groups of the epoxide compounds. In this way, self-crosslinking binders can be synthesized.
• the novel protonized adducts are diluted with water, preferably to a solids content of from 5 to 20% if they are to be used for electrocoating.
• the additives conventionally used in surface coatings eg. other binders, crosslinking agents, pigments, fillers, flow improvers, coupling solvents, catalysts and plasticizers, may be admixed. If the binders have not been rendered self-crosslinking through modification with semi-blocked polyisocyanates, it is advantageous to mix them with crosslinking agents, preferably with from 5 to 40, especially from 15 to 30, % of these, based on solids.
• Suitable crosslinking agents are those possessing functional groups which on baking react with the guanidine and/or amino and/or hydroxyl groups of the binders containing guanidine groups, for example completely blocked polyisocyanates, melamine/formaldehyde resins, phenol/formaldehyde resins, acrylate resins which contain carboxyl groups or N-methylol-ether groups, epoxy resins, polyester resins and alkyd resins.
• the binders obtained using the adducts according to the invention may be employed for coating metals and, if applied by conventional methods, also for coating wood or plastic. They may be applied by conventional methods such as spraying, dipping or casting, but electrocoating is preferred. In the latter method, a d.c. voltage, which may be from a few volt to several 100 volt and is as a rule from 50 to 500 volt is applied, in an aqueous bath, between an immersed anode and the article to be coated, which is wired as the cathode. Coating is allowed to take place until a layer from 10 to 30 ⁇ m thick has been deposited.
• the article is then taken out of the bath, rinsed with water and baked for from 10 to 30 minutes at from 120° to 250° C.
• the electrocoating baths may range from slightly acid to slightly alkaline, a pH of from 6 to 10, especially from 7 to 9, being preferred.
• Working at a neutral pH has the advantage that the coating equipment does not corrode.
• the coatings obtained possess good resilience and excellent resistance to solvents, detergents and caustic alkalis.
• the binders are therefore particularly suitable for coating automotive components and household utensils, as is illustrated by Examples below.
• An epoxide-containing resin suitable for reaction with guanidine is prepared as follows:
• the modification with guanidine is carried out by first adding 100 parts of the above solution of modified epoxy resin, based on a pentaerythritol polyglycidyl ether, dropwise over 50 minutes, at 70° C., to 23.3 parts of a 50% strength by weight solution of guanidine in methanol. The reaction is then allowed to continue for 30 minutes.
• a film is deposited from this binder dispersion at 100 V, over 2 minutes, onto a zinc-phosphatized steel sheet wired as the cathode; after baking for 30 minutes at 180° C., a 28 ⁇ m thick smooth acetone-resistant film results.
• Salt spray test (DIN 50,021): 1 mm rust penetration.
• the binder solution After adding a few drops of tricresyl phosphate, the binder solution is sprayed onto zinc-phosphatized steel sheet and the coating is baked for 30 minutes at 180° C. An acetone-resistant, smooth, glossy coating which withstands flexing is obtained.
• a partially blocked 2,4-toluylene diisocyanate is first prepared by adding 130.2 parts of 2-ethylhexanol to a mixture of 174 parts of 2,4-toluylene diisocyanate and 20 parts of methyl butyl ketone over about 4 hours whilst stirring the mixture under nitrogen and excluding moisture. The reaction temperature is kept below 30° C. After the addition, stirring is continued for 1 hour at 25° C.
• a guanidine-modified self-crosslinking epoxy resin is prepared by adding the total amount of the partially blocked 2,4-toluylene diisocyanate solution, obtained as described above, and 0.1 ml of dibutyl-tin dilaurate to 833 parts of an anhydrous 60% strength solution of a polyglycidyl ether of bisphenol A (epoxide equivalent weight 500) in methyl butyl ketone at 90° C. The reaction is then allowed to proceed for 40 minutes at 120° C.
• the binder After having been neutralized with 60 parts of glacial acetic acid, the binder is introduced into 435 parts of water, with thorough stirring, and the n-butanol is distilled off azeotropically at 30° C. and 30 mbar. The water entrained in the azeotrope is recycled. A milky dispersion having a solids content of 50.6% and a pH of 8.1 is obtained.
• the product As a water-based finish for conventional application, it is diluted to a solids content of 30% with water. The dispersion is then knife-coated onto a zinc-phosphatized steel sheet, air-dried for 5 minutes at room temperature and then baked for 30 minutes at 180° C. An acetone-resistant, smooth, glossy coating is obtained.
• a binder mixture containing epoxide groups and capable of reaction with guanidine is prepared as follows:
• a mixture of 400 parts of a liquid pentaerythritol polyglycidyl ether (epoxide equivalent weight 165), 400 parts of a polyglycidyl ether of bisphenol A (epoxide equivalent weight 500), 91.2 parts of bisphenol A and 37.6 parts of phenol is homogenized under nitrogen at 100° C. 74.4 Parts of mercaptoethanol are then added dropwise over 30 minutes at 100° C. and the reaction is allowed to proceed for a further 30 minutes. 5.0 Parts of tetrabutylammonium iodide are added and the batch is stirred at 100° C. until a plate-and-cone viscosity of 0.5 Pa.s at 150° C. is reached; this requires about 2 hours.
• the mixture is then diluted to a solids content of 60% by weight by adding 669 parts of ethylglycol, and is cooled. Plate-and-cone viscosity of the solution at 75° C.: 0.02 Pa.s. Epoxide value 0.069.
• a film is deposited from this binder dispersion at 120 V, over 2 minutes, onto a zinc-phosphatized steel sheet wired as the cathode; after baking for 30 minutes at 180° C., a 22 ⁇ m thick, smooth, acetone-resistant film which withstands flexing is obtained.
• Salt spray test (DIN 50,021): 1-2 mm rust penetration
• the binder solution After adding a few drops of tricresyl phosphate, the binder solution is sprayed onto zinc-phosphatized steel sheet and baked for 30 minutes at 180° C. An acetone-resistant, smooth, glossy coating which withstands flexing is obtained.
• Pendulum hardness 199

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Health & Medical Sciences (AREA)
• Polymers & Plastics (AREA)
• Medicinal Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Manufacturing & Machinery (AREA)
• Molecular Biology (AREA)
• Paints Or Removers (AREA)
• Polyurethanes Or Polyureas (AREA)
• Epoxy Resins (AREA)

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• 1979
  • 1979-04-07 DE DE19792914085 patent/DE2914085A1/de not_active Withdrawn
• 1980
  • 1980-03-24 US US06/133,437 patent/US4297255A/en not_active Expired - Lifetime
  • 1980-04-03 AT AT80101787T patent/ATE1819T1/de not_active IP Right Cessation
  • 1980-04-03 EP EP80101787A patent/EP0017232B1/fr not_active Expired
  • 1980-04-03 DE DE8080101787T patent/DE3061089D1/de not_active Expired
  • 1980-04-04 JP JP4366380A patent/JPS55135130A/ja active Pending

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